Boosting mechanism for bending wave guide tubing with controlled neutral axis



Jun 3, 1958 v J. F HS, JR 2,8 7, 7

BOOSTING MECHANISM BENDING WAVE GUIDE TUBING WITH CONTROLLED NEUTRAL AXIS Filed May 14, 1953 3 Sheets-Sheet 1 INVENTOR ATTORNEY June 3, 1958 F. J. FUCHS, JR 7,

BOOSTING MECHANISM FOR BENDING WAVE GUIDE TUBING WITH CONTROLLED NEUTRAL AXIS Filed May 14, 1953 5 Sheets-Sheet 2 if I7 I I? INVENTOR fiawali Jma fz;

ATTORNEY 3 She ets-Sheet :5

' a 'h i 1 INVENTOR ATTORNEY June 3, 1958 F. J. FUCHS, JR

BOOSTING MECHANISM FOR BENDING WAVE GUIDE TUBING WITH CONTROLLED NEUTRAL AXIS Filed May 14, 1953 Jag-am amfi In [a M United States Patent ()1 BOOSTING MECHANISM FOR BENDING WAVE GUIDE TUBING WITH CONTROLLED NEU- TRAL AXIS Francis J. Fuchs, Jr., Winston-Salem, N. C., assignor to Western Electric Company, Incorporated, New York, N. Y., acorporation of New York Application May 14, 1953, Serial No. 355,137

8 Claims. (Cl. 153-40) 'tubing is formed to the desired configuration, a clamping die to grip the tubing and to prevent lateral displacement of the forward end of the tubing during the bending operation, and pressure and wiper dies to prevent lateral displacement of the rearward extremity of the tubing. The forming and clamping dies are mounted on a single rotatable support and comprise a bending head.

In draw bending thin walled tubing, the metal of the tubing walls is subjected to compressional and tensional forces, the metal of the inner wall of the bend being compressed and the metal of the outer wall of the bend being stretched, the latter process resulting in a reduction of the wall thickness with the accompanying likelihood of tearing. In a draw bending operation the metal of the tubing is also subjected to the additional tensional force necessary to pull the tubing through the bending die.

The hypothetical dividing line between the compressional and tensional forces is known as the neutral axis of the tubing being bent. Ideally, the neutral axis should be kept coincident with the center line of the tubing, thus giving equal amounts of tension and compression and which best can be accomplished by equalizing the pushing and pulling forces on the tubing as it passes through the bending dies. For this purpose a booster is provided to engage the rearward extremity of the tubing being bent and to exert upon it the necessary pushing force to balance the tensional force necessary to pull the tubing through the dies.

Boosting mechanisms for this purpose have been provided in the past but the greatest objection to their use has been the lack of synchronization of the rate of for, ward movement ofthe booster with the rate of travel of the tubing through the bending dies. Various methods have been attempted to overcome this undesirable feature such as the interposition of tensioned springs, use of a separate fluid pressure actuating means controlled by a variable pressure pump, and clutching the booster mechanism to the operating mechanism of bending dies. These attempts often have failed either to achieve the desired perfection of synchronization of the rate of travel of the booster mechanism with that of the tubing or have involved unduly complicated or cumbersome additions to or modifications of the bending machine.

Accordingly, it is an object of the present invention to provide a simplified boosting mechanism which may be readily attached to a standard bending machine and which will provide a high degree ofcooperative movement between the boosting mechanism and the tube being bent.

2,837,137 Patented June 3, 1958 It is a further object of the present invention to provide a boosting mechanism whereby the same force used to actuate the bending head and to pull the tubing through the dies is utilized to exert a balancing pushing force on the rearward extremity of the tubing being bent.

It is another object of this invention to provide a readily adjustable boosting mechanism whereby the length of tubing to be bent may be readily and accurately controlled.

In accordance with the above objects, a preferred embodiment of the present invention comprises, in a machine for bending tubing, a rotatable bending head, a longitudinally movable pressure die, a rotatable sprocket and chain drive mechanism to actuate the bending head, means to actuate the drive mechanism, and a boosting mechanism comprising a booster head engageable with the rearward extremity of the tubing to be bent, a transversely positioned extensible arm connected at one end to the booster head and 'at the other end to a connecting block which is attached to the longitudinally movable drive mechanism. The extensible arm is pivoted on a pivot block at a transversely adjustable position intermediate of the length of the arm whereby the longitudinal force of the driving mechanism is transmitted to the booster head, the longitudinal displacement thereof being dependent upon the distance of travel of the driving mechanism and the transverse adjustment of the pivot block.

Other features and advantages of the present invention will become more apparent from the following detailed description, when taken in conjunction with the accompanying drawings, in which Fig. 1 is a partially fragmentary perspective view of a tube bending machine showing the boosting mechanism in its assembled position;

, Fig. 2 is a plan view of the partially assembled boosting mechanism;

Fig. 3 is an elevational view, partly in cross section,

of the boosting mechanism taken on line 33 of Fig. 2;

Fig. 4 is an elevational view of the boosting mechanism taken on line 4-4 of Fig. 2;

Fig. 5 is a cross sectional plan view of the pivot adjusting means of the boosting mechanism taken on line 55 of Fig. 3;

Fig. 6 is a cross sectional elevational view of the extensible arm and the associated pivot block taken on line 6-6 of Fig. 2, and

Fig. 7 is a cross sectional elevational view of the connecting block by means of which the extensible arm is attached to the drive mechanism and is taken along line 77 of Fig. 2.

Referring now to the drawings, wherein like reference numerals designate the same elements throughout the several views, and more particularly to Figs. 1, 2, and 4 which illustrate the boosting mechanism mounted upon the bending machine, Fig. 1 shows, in dotted lines, a piece of rectangular wave guide tubing 10 in pro-bending position between a forming die 12, a clamping die 13, a pressure die 14, and a wiping die 15. A fluid pressure cylinder 16 is mounted toward the rear of the bending machine and slidable therein is a piston (not shown) and connected thereto is a piston rod 17, the latter carrying a supporting mandrel (not shown) on the free 23 mounted upon a rotatable shaft 24 which may be driven by an electric motor 25. The two sprockets 22 and 23 are connected operatively by. a substantially continuous loop consisting of a roller-type sprocket chain 26 which is connected operatively in series with a fiuid pressure cylinder 27 having slidable therein a double acting piston 63 with an associated piston rod as at 2%. The cylinder 27 is'secured fixedly to the bending machine and one end of the piston rod 28 is secured by any suitable means such as a pin 29 within a recess 21 in one side of a connecting block indicated generally by the numeral 30. Chain 26 is longitudinally aligned with the piston rod 23 and one end thereof is secured Within a recess 31 in the other side of the connecting block by any suitable means such as a pin 32. The other end of the chain 26 is attached to the opposite end of the piston rod 28. The connecting block in the embodiment ShOWn is composed of an upper member 33 and a lower member 34.

which are secured together by bolts 35. Projecting from the two portions of the connecting block are opposing tongues 36 which are slidably movable in grooves 37 in a track 38 which is attached to the front wall of the bending machine by bolts 41. Attached to the rear wall of the bending machine is a guide rod 39 upon which is slidably mounted a booster head indicated generally by the numeral 40.

Suitable hydraulic means (not shown) are provided for controlling the operation of the cylinder 27 to operate the chain 26 and thereby to rotate the sprockets 22 and 23 through a predetermined angular rotation. It will be understood that the electric drive motor 25 and cylinder 27 are merely alternative means for driving the sprockets 22 and 23.

The booster head 40 consists of a slide member having two depending legs 42 which are longitudinally movable upon guide rod 39 and to which is connected a plate 43 upon which is mounted two upright projections 44. An extensible arm indicated generally by the numeral 45 consists of an upper tongued member 46 and a lower grooved member 47. One end of the upper member is attached pivotally to an upright leg 42 of the slide mem-' bet as by pivot pin 48, and the lower member is attached pivotally at the other end to the connecting block 3t) as by pin 49. Pivot pins 48 and 49 are held in place by pins 59 and 51, respectively.

A frame indicated generally by the numeral 52 is mounted on the bending machine underneath the extensible arm and has two parallel, transversely extending guide members 53 between which is slidably movable a supporting plate 54 having therein a threaded passage 55 in which is positioned a threaded member 56 which is attached to the frame 52 and to the wall of the bending machine, and by means of which the transverse position of the supporting plate 54 may be adjusted. A pivot pin 57 is mounted vertically in an aperture 58 in the supporting plate. A pivot block 59 is mounted upon and rotatable about the pivot pin 57 and is adapted to engage the upper member 46 of the extensible arm by means of a tongue 6%) sliding in a groove 61 in member 46. (Fig. 6.)

To adjust the machine for making a desired bend in a piece of tubing, the bending head I? is rotated initially to its 90 angular position, in which position the forward edge of the booster head 4!) coincides with a reference line 62 provided, for convenience, on the guide rod 39. With the bending head 19 held in its 90 angular position, the extensible arm 45 assumes a position such that its longitudinal axis is perpendicular to the path of travel of the connecting block 31). The bending head 1? next is returned to its zero angular position and by adjusting the threaded member 56, the booster head 44} is moved so that at this angular position of the bending head the leading edge of the booster head is at a distance L (Fig. l) from the reference line 62-. Assuming that it is desired to hold the neutral axis of the bend at the centerline of the tubing, the distance L must be equal to the centerline length for a 99 bend, that is, 1.:2112 (90/360),

4 where R is the centerline radius of the bend. With the bending machine set up as described hereinabove, any angular bend a may be imparted to a piece of tubing without further adjustment, provided that there is no change in the centerline radius. Manifestly, the centerline radius will differ for various widths of tubing.

In operation, assuming that a bend of oc is to be formed, the bending head is rotated through a. The tubing is engaged directly or by means of a connecting sleeve (not shown) against the projections 44, and is advanced between the bending dies for the distance L=21rR (CL/360) and at the same rate at which the front end of the tubing is being pulled through the dies. Thus, by accurately controlling the length of the bend and the boosting of the tubing through the dies, the neutral axis thereof is controlled.

It is to be understood that the above-described arrangements are simply illustrative of the invention. Numerous other modifications may be devised by those skilled .in the art without departing from the spirit and scope of the invention. 7

What is claimed is:

1. In a machine for draw bending tubing,'a rotatable forming die, means to secure the tubing in the forming die, means to actuate the forming die, a reciprocable mandrel, means to support and actuate the mandrel, a slide mounted on the bending machine, engaging means mounted on the slide and adapted to contact the rearward extremity of the tubing being bent and to allow passage therethrough of the mandrel supporting and actuating means, an extensible arm pivotally connected at one end to the forming die actuating means and at the other end to the slide, and a support member upon which the extensible arm is mounted pivotally for rotational movement about a fulcrum point intermediate of the ends of the arm, said support member being adjustably positionable to shift the fulcrum point with respect to the ends of said arm.

2. In a tube bending machine having a rotatable bending head and a longitudinally movable drive means to rotate the head, a boosting means to push a predetermined length of tubing through the bending head, said boosting means comprising a booster head engageable with the rearward extremity of the tubing being bent, a tongued and grooved extensible arm pivotally connected at opposite extremities thereof to the booster head and to the drive means, respectively, and a support member upon which the extensible arm is mounted pivotally for rotationalmovement about a fulcrum point intermediate the opposite extremities of the arm, said support member beingadjustably positionable in a direction transverse to the longitudinal movement of said drive means to shift the fulcrum point with respect to the extremities of the arm whereby the length of the tubing pushed into the bending head for a predetermined rotation of the bending head may be preselected.

3. In a tube bending machine, a first spindle, abending head mounted on the first spindle, a first sprocket wheel mounted on the first spindle, a second spindle, a second sprocket wheel mounted on the second spindle, chain means extending between and around the sprocket wheels, means for driving the chain to rotate the bending head through a predetermined angle, a booster head slidably mounted on the bending machine and adapted to engage the rearward extremity of the tubing being bent, an extensible arm pivotally connected at one end to the chain means for movement therewith and at the other end to the booster head, a support member upon which the extensible arm is mounted pivotally for rotational movement about a fulcrum point intermediate of the ends of the arm, said support member being adjustably positionable to shift the fulcrum point with respect to the ends of said arm, whereby the distance of travel of the booster head may be Varied for a given length of travel of the end of the arm attached to the chain means.

4. In a tube bending machine, a rotatable driven shaft, a bending head mounted on the driven shaft, a driving shaft parallel to and longii :dinally displaced from the driven shaft, looped chain drive means extending between the driven shaft and the driving shaft, means for actuating said drive means to rotate the bending head through a predetermined angle, first and second guide means mounted on the bending machine in parallel and spaced relationship, a connecting block slidably mounted on the first guide means and operatively connected to the drive means for movement therewith, a booster head slidable on the second guide means and adapted to engage the rearward extremity of the tube to be bent, an extensible arm pivotally connected at one end to the connecting block and at the other end to the booster head, and a support member upon which the extensible arm is mounted pivotally for rotational movement about a fulcrum point intermediate of the ends of the arm, said support member being adjustably positionable to shift the fulcrum with respect to the ends of said arm whereby the distance of travel of the booster head may be varied for a given length of travel of the end of the arm attached to the connecting block.

5. In a tube bending machine, a rotatable forming die, means to clamp the tube to the forming die, a driven shaft connected to the forming die, a first sprocket mounted on the driven shaft, a driving shaft, a second sprocket mounted on the driving shaft, a substantially continuous roller chain extending around and between said first and second sprockets, a fluid pressure cylinder, a double acting piston slidable in the cylinder and connected in series with the roller chain, a track mounted in a longitudinal position on the bending machine, a connecting block slidably mounted on the track, said block being connected at one end to the piston and at the other end to the roller chain, a guide rod mounted on the bending machine in a position parallel to the track and laterally displaced therefrom, a booster head slidable on the guide rod, said booster head being adapted to engage the rearward extremity of the tube being bent, an extensible arm pivotally connected at one end to the connecting block and at the other end to the booster head, an adjustable supporting plate slidably mounted on the bending machine underneath the extensible arm, means to adjust the transverse position of the supporting plate, a vertical pivot pin mounted in the supporting plate, and a pivot block mounted on the supporting plate and rotatable about the pivot pin, said pivot block being adapted to slidably en'- gage the extensible arm.

6. In a tube bending machine, a rotatable forming die, means to clamp a tube to the forming die, means to actuate the forming die, means for engaging a rearward extremity of the tube and urging the tube longitudinally toward the forming die to boost the tube around the forming die, a member mounted on the bending machine and adjustable transversely with respect to the direction in which the tube engaging means urges the tubing, and extensible means for actuating the tube engaging means,

said extensible means being pivotally connected at one extremity thereof to the tube-engaging means, at the other extremity thereof ttthe forming die actuating means, and intermediate of said extremities to said adjustable member.

7. A tube bending machine which comprises a rotatable bending head for bending metal tubing, a drive shaft on which the bending head is secured for rotation therewith, an elongated loop of chain connected operatively to the drive shaft, drive means for operating the chain to cause a predetermined rotation of the bending head to bend the tubing, and a booster mechanism comprising a booster head engageable with the rear extremity of the tubing being bent for urging the tubing longitudinally toward the bending head, an extensible arm pivotally connected at one extremity thereof to the booster head and the other extremity to a portion of the chain loop arranged to move generally in a direction longitudinally away from the bending head and means to pivot the extensible arm adjustably intermediate of the extremities thereof to vary the longitudinal displacement of the booster head relative to the movement of the chain.

8. In a machine for draw bending tubing, a longitudinally movable pressure die, a forming die, a clamping die, a first rotatable shaft upon which said forming die and clamping die are mounted at one extremity of the bending machine, a first sprocket mounted horizontally on the first rotatable shaft, a second rotatable shaft lo cated at the other extremity of the bending machine, a second sprocket mounted horizontally on said second rotatable shaft, a substantially continuous drive chain extending longitudinally in two parallel lengths between the first and second sprockets, a longitudinally movable connecting block connected in series with one of the parallel lengths of the drive chain, means for actuating said drive chain to rotate the first shaft through a predetermined angle, a booster head designed to engage the rearward extremity of the tubing being bent and to urge the tubing toward the forming die, an extensible arm pivotally connected at one end to the connecting block and at the other end thereof to the booster head, and a support member upon which the extensible arm is mounted pivotally for rotational movement about a fulcrum point intermediate of the opposite ends of the arms, said support member being adjustably positionable in a direction transverse to the longitudinal movement of the connecting block to shift the fulcrum point with respect to the ends of the arm whereby the length of the tubing pushed into the bending head for a predetermined rotation of the bending head may be preselected.

References Cited in the file of this patent UNITED STATES PATENTS 1,013,839 Cox Jan. 2, 1912 1,105,914 Miller Aug. 4, 1914 2,306,224 Parker et al. Dec. 22, 1942 2,357,873 Bower Sept. 12, 1944 

